In response to certain wavelengths of electromagnetic radiation (or “actinic radiation”), photochromic compounds, such as indeno-fused naphthopyrans, typically undergo a transformation from one form or state to another form, with each form having a characteristic or distinguishable absorption spectrum associated therewith. Typically, upon exposure to actinic radiation, many photochromic compounds are transformed from a closed-form, which corresponds to an unactivated (or bleached, e.g., substantially colorless) state of the photochromic compound, to an open-form, which corresponds to an activated (or colored) state of the photochromic compound. In the absence of exposure to actinic radiation, such photochromic compounds are reversibly transformed from the activated (or colored) state, back to the unactivated (or bleached) state. Compositions and articles, such as eyewear lenses, that contain photochromic compounds or have photochromic compounds applied thereto (e.g., in form of a photochromic coating composition) typically display colorless (e.g., clear) and colored states that correspond to the colorless and colored states of the photochromic compounds contained therein or applied thereto.
Photochromic compounds can be incorporated into a polymeric matrix, which can result in the formation of a photochromic article, such as a photochromic ophthalmic lens, including, but not limited to photochromic contact lenses. With photochromic contact lenses, for example, it is typically desirable that the photochromic compound undergoes minimal to no migration out of the contact lens matrix, such as into a cleaning solution and/or a human eye. Additionally, in some applications it is desirable that the photochromic compound undergo minimal to no migration within the contact lens matrix, such as from a central or pupil area of the lens out into the surrounding matrix area thereof.
It would be desirable to develop new indeno-fused naphthopyran compounds that are photochromic, and which undergo minimal to no migration within and/or out of a polymeric matrix into which they are incorporated. Additionally, it would be desirable that such newly developed indeno-fused naphthopyran compounds possess photochromic properties, such as but not limited to, fade rate and/or optical density properties, that are at least the same as those of conventional indeno-fused naphthopyran compounds.